Hydraulic and earth engineering – Bank – shore – or bed protection – Revetment
Patent
1980-12-22
1983-09-20
Taylor, Dennis L.
Hydraulic and earth engineering
Bank, shore, or bed protection
Revetment
405 18, E02B 312
Patent
active
044052570
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a safety mat used for protection of areas against erosion and/or undermining by the action of water, which mat consist of a number of parallel tubular members containing a filling material and being mutually connected by cross-binding ribbons placed at right angles to the tubular members and progessing about same forming a woven mat.
A safety mat of this type is known from the German published patent specification No. 2,762,692. In the case of this known mat the parallel casings or tapes are filled as tightly as possible, which hitherto has been considered the most appropriate, as it was desired to produce as heavy a mat as possible in order to avoid it being washed away.
However, it has turned out that this type of tightly filled mats is not a sufficiently effective protection of the waterwashed areas, as openings from between the hard and rigid casings making considerable passage of water possible from the upper side of the mat to the bottom side, whereby the material under the mat from time to time is washed away. The rigid casings are self-supporting and form a bridge over the pockets that are hollowed out under the mat by the washing away, and after some time the mat will rest on only a few tops. When a mat resting in this manner is exposed to a violent passage of water the mat will be torn away by the sea. This invention is based on a recognition of the above mentioned conditions with known safety mats, and the object of the invention is to design a safety mat which can be laid out directly on the area to be protected and which permanently and effectively protects against washing away.
According to the invention, this object is achieved by a safety mat of the type mentioned in the introduction and characterized in that the filling material is a granulated material of an average density of at least 1.6 kg/dm.sup.3, and that the degree of filling of the tubular members is substantially 75%.
By using a filling material of a relatively large density (>1.6) which is introduced fairly loosely in the parallel tubular members (degree of filling ab. 75%) a mat is obtained that is heavy, but at the same time very flexible and capable of adopting the form of the bottom surface even if it should be a very domed surface. Even if when using such a mat a certain passage from the top to bottom should occur, this would not result in the aforementioned openings under the mat, as the yielding tubular members sink and contact the new bottom surface.
According to the invention the filling material can be a mixture of one or more relatively heavy materials and one or more relatively light materials. In this manner it will be possible, when laid out under water, to utilize the buoyancy of the water to administer to the mat a cross-sectional form appropriate for its particular use.
In a preferred embodiment the filling material is a mixture of pearl gravel and polystyrene granules. These easily acessible materials allow the passage of water and the grain size is sufficiently large to prevent them from penetrating a finely woven tubular member material at the same time preventing silting of the inside of the member.
According to the invention the pearl gravel can be placed at the ends of the tubular member, while the polystyrene is placed in the middle of the member. In this manner, the mat, when placed under water, as a result of the buoyancy will assume a reversed U-form in cross-section, and can therefore be used for protection of, for instance, tubular conduits laid out on the sea bed, or used to form a sort of tunnel on the sea bed.
In an embodiment preferred in practice the tubular members are provided with radially extending flaps situated diametrically opposite each other, said flaps being slightly pliable. It has been shown that these flaps rest against each other at two adjacent members, whereby a greater density is obtained in the mat and correspondingly greater security against the passage of water from the top to the bottom of the mat.
By providing for the cross-binding tapes being st
REFERENCES:
patent: 984121 (1911-02-01), Condie
patent: 2047197 (1936-07-01), Fordyce
patent: 3474626 (1969-10-01), Colle
patent: 3561219 (1971-02-01), Nishizawa et al.
patent: 3696623 (1972-10-01), Heine et al.
patent: 3837169 (1974-09-01), Lamberton
patent: 4102137 (1978-07-01), Porraz et al.
Daekko Presenning Kompagni A/S
Taylor Dennis L.
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